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Reflectance and photoluminescence spectra of as grown and hydrogen and nitrogen incorporated tetrahedral amorphous carbon films deposited using an S bend filtered cathodic vacuum arc process |
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| Authors: | OS Panwar Mohd Alim Khan B Bhattacharjee BS Satyanarayana R Bhattacharyya |
| Affiliation: | a Plasma Processed Materials Group, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012, India b Department of Materials Science, Indian Association for the Cultivation of Science, Kolkata 700 032, India c MIT Innovation Center and Electronics and Communication Department, Manipal Institute of Technology, Manipal-576104, India d Emeritus Scientist National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012, India e Department of Physics, Jamia Millia Islamia, Central University, New Delhi 110025, India |
| Abstract: | The study of reflectance and photoluminescence (PL) spectra of as grown and also hydrogen and nitrogen incorporated tetrahedral amorphous carbon (ta-C) films, deposited using an S bend filtered cathodic vacuum arc process is reported here. First the effect of negative substrate bias on the properties of as grown ta-C films and next the effect of varying hydrogen and nitrogen partial pressure at a high substrate bias of − 300 V on the properties of hydrogen and nitrogen incorporated ta-C (ta-C:H and ta-C:N) films are reported for the first time. The values of the optical band gap (Eg) evaluated using the reflectance spectra were found to decrease with the increase of the substrate bias in the as grown ta-C films. Hydrogen incorporation up to 1.9 × 10− 2 Pa partial pressure in as grown ta-C films increased the values of Eg and beyond which the values of Eg decreased while the nitrogen incorporation up to 3.0 × 10− 1 Pa partial pressure has no effect on the Eg values. The PL spectra indicated a strong peak at ∼2.66 eV in as grown ta-C films deposited at − 20 V substrate bias. This main peak was found to shift to higher energy with the increase of the substrate bias up to − 200 V and thereafter the PL peak shifted towards the lower energy. Other peak at 3.135 eV starts appearing and this is found to start shifting to higher energy for films deposited at higher substrate bias. The intensity of the main PL peak was enhanced at low temperature and several other peaks started appearing in place of the broad peak at ∼3.16 eV. The peak width and area of both the main peak were found to decrease with the increase of substrate bias in as grown ta-C films and with the increase of the hydrogen and nitrogen partial pressure used in depositing ta-C:H and ta-C:N films. The current models on the source of luminescence in amorphous carbon have been discussed. |
| Keywords: | Amorphous materials Carbon Optical properties Photoluminescence Deposition-process ta-C:N Filtered cathodic vacuum arc |
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